TW201333930A - Method of fabricating bow stick of stringed instrument and bow stick of stringed instrument - Google Patents

Abstract

A method of fabricating a bow stick includes winding a prepreg, in which a fiber is impregnated with a resin, on a mandrel with a diameter gradually decreasing toward a distal end, setting a semi-fabricated product, in which the prepreg is wound on the mandrel, into a mold and molding the semi-fabricated product in a shape corresponding to a cavity formed between the mold and the mandrel by heating and pressurizing the semi-fabricated product in the mold, and taking out the mandrel from a molded product molded in the shape corresponding to the cavity to acquire a long and hollow stick body. When adjusting at least one of a weight distribution, a center of gravity, and a weight of the stick body, the volume of the cavity is changed using the mandrel of which the diameter or the diameter variation is gradually changed in an axis direction.

Description

Method for manufacturing a bow of a stringed instrument and a bow of a stringed instrument

The invention relates to a method for manufacturing a drawbar of a stringed instrument and a drawbar for a stringed instrument.

The priority of Japanese Patent Application No. 2011-241461, filed on Nov. 2, 2011, is hereby incorporated by reference.

Conventionally, wooden drawbars (rods) have been used as bows for stringed instruments such as violins, violas, cellos or double basses. Pernambuco wood, which is particularly hard, dense, moisture resistant and has excellent bending strength, has been used as a material suitable for pulling the bow. However, the availability of Pernambuco has been greatly reduced due to deforestation and it is difficult to obtain Pernambuco due to current international trade restrictions.

Therefore, as an alternative to a drawbar formed of wood (such as Pernambuco), fiber-reinforced plastic (FRP) (such as carbon fiber reinforced plastic (CFRP) or glass fiber reinforced plastic (using a composite of fiber and resin) GFRP)) The formed bow has been developed (for example, see Japanese Patent Publication No. S44-19189).

Since the wooden drawbars are cut from the wood and finished by hand, it is not possible to make the exact same rod. However, since the FRP pull rod is made of the same material and mold, it is possible to manufacture the same rod in the industry with excellent reproducibility. When manufacturing wooden drawbars, it is difficult to adjust, for example, the weight distribution, center of gravity, and weight of the drawbar without changing the outer shape or size due to the difference in density of the wood as a natural material.

As a method of producing a hollow fiber reinforced resin molded product, a method called an internal pressure molding method is known (for example, see Japanese Unexamined Patent Application Publication No. H11-48318). In the internal pressure molding method, a prepreg impregnated with a fiber by a non-curing resin is wound around a pressurizing bag formed of a flexible material and the resultant is placed in a mold. Subsequently, the mold is clamped and then heated while the pressurized bag is inflated to push the prepreg into the inner surface of the mold. Therefore, the prepreg can be shaped to correspond to the shape of the cavity formed between the mold and the pressurized bag.

However, in the manufacturing method of the hollow fiber reinforced resin molded product using the internal pressure molding method, since the prepreg is moved into the mold while the pressurized bag is inflated, the expansion of the pressurized bag may be uneven.

Therefore, when the drawbar is manufactured by the internal press molding method, the shape of the cavity is not constant each time the molding is performed and the weight distribution or the center of gravity of the molded drawbar is uneven.

In another aspect, the inventors of the present invention have proposed a method of molding a hollow structural product in which an FRP prepreg is wound around a columnar metal mandrel having a tapered end and capable of rebounding, and the FRP prepreg is wrapped around it. The mandrel is placed in a mold having a cavity outside the hollow structure product, and the mold is heated to obtain a molded product and then the mandrel is removed therefrom (for example, see Japanese Patent No. 3541756).

When the drawbar is manufactured using a method of molding a hollow structural product, the shape of the cavity formed between the mold and the mandrel can be kept uniform for each molding during molding. Therefore, the weight distribution of the molded drawbar or the unevenness of the center of gravity can be prevented.

The user (stringed instrument player) experience varies depending on the weight distribution of the bow of the stringed instrument, the center of gravity, the weight, and the like. Therefore, when fabricating a drawbar formed of FRP, it is necessary to prepare a plurality of drawbars that finely adjust the weight distribution, center of gravity, weight, and the like of the drawbar based on the user's experience.

The present invention has been made in view of such circumstances and its object is to provide a method for making a bow of a stringed instrument which can be finely adjusted and easy to adjust the weight distribution, center of gravity and weight of the drawbar, and a stringed instrument whose weight distribution, center of gravity and weight are precisely adjusted. Pull the bow.

According to an aspect of the present invention, there is provided a method of producing a drawbar for a stringed instrument and formed of a fiber reinforced plastic, comprising the steps of: winding a prepreg in which a fiber is impregnated with a resin to a tip end and gradually decreasing in diameter a small diameter mandrel; a semi-finished product formed by winding a prepreg on a mandrel into a mold; the semi-finished product is molded to correspond to the mold and the heart by heating and pressurizing the semi-finished product in the mold The shape of the cavity between the shafts; the mandrel is taken out from the molded product molded to the shape corresponding to the cavity to obtain a long and hollow rod; and gradually changed in the axial direction by using a change in diameter or diameter The mandrel changes the shape of the cavity and adjusts at least one of the weight distribution, the center of gravity, and the weight of the drawbar of the body.

According to another aspect of the present invention, there is provided a drawbar for a stringed instrument and a stringed instrument formed of fiber reinforced plastic, comprising a rod having a reduced diameter toward the distal end and molded into a long and hollow shape Body in which the rod body is pulled by gradually changing the diameter or diameter of the shaft hole in the axial direction At least one of the weight distribution, center of gravity and weight of the bow.

As described above, in the manufacturing method of the bow of the stringed musical instrument according to the aspect of the present invention, the volume of the cavity can be changed without changing the mold by using a mandrel whose diameter or diameter changes gradually in the axial direction. The fine adjustment and easy adjustment of the weight distribution, center of gravity and weight of the molded body in the mold.

In the pull rod of the stringed instrument according to the aspect of the present invention, the weight of the shaft can be accurately adjusted without changing the outer shape or size of the shaft by gradually changing the diameter or diameter of the shaft hole in the axial direction. Distribution, center of gravity and weight.

Hereinafter, a method of manufacturing a drawbar of a stringed instrument according to the present invention and a drawbar of a stringed instrument will be described in detail with reference to the accompanying drawings.

In the drawings referred to in the following embodiments, in order to facilitate the understanding of the features, the features are schematically illustrated and the scale of the elements is said to be unrealistically identical. The materials, sizes, and the like exemplified in the following embodiments are merely examples and the invention is not limited to the examples. The invention can be modified as appropriate without departing from the concept of the invention.

In one embodiment of the invention, the bow of the stringed instrument shown in Figure 1 is used for stringed instruments, such as violins, violas, cellos and double basses, and is referred to as a carbon bow, which is replaced by a pull rod 1 formed, for example, by CFRP. A pull rod (rod) formed of wood such as Pernambuco.

In the bow of the stringed instrument shown in Fig. 1, the bowstring 3 is mounted between the head 1a disposed on the distal end H of the drawbar 1 and the arch 2 disposed on the outer circumference of the bottom end B and the bowstring 3 Tension can be placed at the bottom end of the rotating pull rod 1 Adjust with the screw 4 on it.

As shown in FIGS. 2A to 2C, the pull rod 1 includes a rod 1A having a long and hollow shape and forming a main body together with the head 1a. The rod body 1A has an arcuate shape bent back to the opposite side to the mounting side of the bowstring 3 and can be bent (elastically deformed) in the opposite direction of the bending return direction when the bow string 3 is mounted.

As shown in Fig. 2A, the rod body 1A has an outer shape in which the distal end H is entirely thinner than the bottom end B except for the head portion 1a. As shown in Fig. 2B, the cross section of the rod body 1A has a substantially circular shape in the axial direction, but one of the bottom ends has a substantially octagonal shape as shown in Fig. 2C to improve the bending strength (rigidity) of the rod body 1A. Or structural.

An axial hole 1b having a substantially circular cross section is formed on the center of the rod body 1A in the axial direction. The axial hole 1b has a so-called tapered shape, and the diameter gradually decreases from the bottom end B to the distal end H to correspond to the outer shape of the rod body 1A (Φ ₁ <Φ ₂ ).

The shape of the rod 1A shown in FIGS. 2A to 2C is merely an example and the rod body 1A can appropriately change the thickness or the cross section at various positions in the axial direction in consideration of bending strength (stiffness), structurality, and the like. The shape is formed into an appropriate shape.

A method of manufacturing the drawbar 1 will be described below with reference to FIGS. 3 to 7.

As shown in (a) and (b) of FIG. 3, when the drawbar 1 is produced, the prepreg 11 is first wound around the mandrel 10.

The mandrel 10, together with the mold 20 shown in Figure 5, defines a space (cavity) for shaping the wound prepreg 11 into the drawbar 1, and will be described below and can be rebounded by way of example. form. The mandrel 10 has a tapered shape, and the diameter gradually decreases from the bottom end B to the distal end H to form an axial hole of the rod body 1A. 1b.

The prepreg 11 is a carbon fiber impregnated with a non-curing thermosetting resin. Examples of the prepreg 11 include fibers in which carbon fibers are disposed in one direction and impregnated with a thermosetting resin; fibers in which plain weave, twill weave or satin weave carbon fibers are impregnated with a thermosetting resin; and fibers in which short fiber carbon fibers are cured with a thermosetting resin. Examples of the thermosetting resin include an epoxy resin and an unsaturated polyester resin.

In the present embodiment, the area of the prepreg 11 wound on the mandrel 10 is adjusted in the axial direction to correspond to the shape of the cavity. Specifically, the weight of the drawbar 1 formed by the prepreg 11 is adjusted to correspond to the size (volume) of the cavity by changing the winding width distribution of the prepreg 11 wound on the mandrel 10.

As shown in (a) of FIG. 3, the weight of the molded rod 1A can be changed based on the area of the prepreg 11 wound on the mandrel 10. That is, when the thickness of the mandrel 10 is decreased to increase the area of the prepreg 11, the number of prepregs 11 wound on the mandrel 10 can be increased to increase the weight of the molded body 1A. On the other hand, when the thickness of the mandrel 10 is increased to reduce the area of the prepreg 11, the number of prepregs 11 wound on the mandrel 10 can be reduced to reduce the weight of the molded body 1A. .

The weight distribution and center of gravity of the molded rod 1A may vary depending on the shape of the prepreg 11 wound on the mandrel 10 (i.e., the winding width distribution). That is, as shown in FIG. 3(b), the molded rod body 1A can be adjusted in weight distribution and center of gravity by providing the inclined portion 11a to the distal end H of the prepreg 11 and the position or angle of the inclined portion 11a. .

The relationship between the shape of the mandrel 10 and the prepreg 11 and the center of gravity of the molded rod body 11A will be described below with reference to FIG.

When the prepreg 11-2 having the sectional shape shown in the second example E2 is wound around the mandrel 10-2 having the flat shape shown in the second example E2 in Fig. 4, the molded rod 1A is to be molded. The center of gravity is located at position G2.

As shown in the first example E1, when the center of gravity is molded by the rod at a position G1 closer to the bottom end B than the position G2, the distal end H of the mandrel 10-1 is set thicker than the mandrel 10-2. Further, the winding width distribution of the prepreg 11-1 is changed so that the width of the bottom end B is set larger than the width of the prepreg 11-2 and the width of the distal end H is smaller than the width of the prepreg 11-2. The winding width distribution of the prepreg 11-1 may also be changed so that only the width of the bottom end B is set to be larger than the width of the prepreg 11-2 or only the width of the tip end H is set to be smaller than that of the prepreg 11-2. width. The rod body 1A formed by winding the prepreg 11-1 on the mandrel 10-1 has the same outer shape as the second example E2 but whose center of gravity is located at a position G1 closer to the bottom end B.

As shown in the third example E3, when the center of gravity is molded on the rod at a position G3 closer to the distal end H than the position G2, the bottom end B of the mandrel 10-3 is set thicker than the mandrel 10-2. Further, the winding width distribution of the prepreg 11-3 is changed so that the width of the bottom end B is set to be smaller than the width of the prepreg 11-2 and the width of the distal end H is set larger than the width of the prepreg 11-2. The winding width distribution of the prepreg 11-3 may also be changed so that only the width of the bottom end B is set to be smaller than the width of the prepreg 11-2 or only the width of the tip end H is set to be larger than that of the prepreg 11-2. width. The rod body 1A formed by winding the prepreg 11-3 on the mandrel 10-3 has the same outer shape as the second example E2 but the center of gravity is located at Near position G3 of the tip end H.

When the winding width distribution of the prepreg 11 is adjusted, the prepreg 11 subdivided into a plurality of portions may be stacked and wound on the mandrel 10 to obtain a winding width distribution corresponding to the area and shape of the prepreg 11. In this case, the number of prepregs 11 wound on the mandrel 10 can be adjusted in the axial direction.

As shown in (a) of FIG. 6, the semi-finished product 1B formed by winding the prepreg 11 on the mandrel 10 is installed in the mold 20.

As shown in FIGS. 5 and 6(a) and (b), the mold 20 defines the outer shape of the rod 1A (the pull rod 1) and includes one of the lower mold 21 and the upper mold 22 which are vertically divided in the vertical direction. The lower mold 21 and the upper mold 22 mold the rod body 1A (the pull rod 1) in a concave portion 21a and 22a which are symmetrical with the partition plane in the axial direction and correspond to the outer shape of the rod body 1A (the pull rod 1). Its opposite surface.

The mold 20 forms a space corresponding to the outer shape of the rod body 1A by causing the concave portions 21a and 22a to face each other when the lower mold 21 and the upper mold 22 are assembled to each other.

The lower mold 21 and the upper mold 22 have the same shape, and the concave portions 21a and 22a are formed symmetrically. Only one mold 20 (lower mold 21) is shown in FIG.

The mold 20 is clamped by placing the semi-finished product 1B into the concave portion 21a of the lower mold 21 as shown in Fig. 6(b), and then the lower mold 21 and the upper mold 22 are assembled to each other as shown in Fig. 6(a).

At this time, a cavity S having a shape corresponding to the rod body 1A (pull rod 1) is formed between the mold 20 and the mandrel 10. The semi-finished product 1B fills the mold 20.

After the clamp, the semi-finished product 1B is heated and pressurized in the mold 20. Therefore, the thermosetting resin in the prepreg 11 of the semi-finished product 1B is cured to allow prepreg The body 11 is molded to correspond to the shape of the cavity S.

As shown in (a) and (b) of Fig. 7, the mandrel 10 is then taken out from the molded body, i.e., the rod 1A, molded into a shape corresponding to the cavity S. Subsequently, the rod body 1A (the pull rod 1) can be released from the mold 20 by releasing the assembly of the lower mold 21 and the upper mold 22. The mandrel 10 can be taken out from the shaft 1A after the rod 1A is released from the mold 20.

Through these processes, the drawbar 1 shown in Fig. 2A can be produced.

Although not shown in the drawings, the head 1a of the drawbar 1 is placed into the mold 20 by the semi-finished product 1B formed by winding the prepreg on the core, and then the semi-finished product together with the semi-finished product 1B in the mold 20 is heated and It is press molded to form a body together with the rod body 1A.

In the manufacturing method of the pull rod 1, the volume and shape of the cavity S are gradually changed in the axial direction when the weight distribution, the center of gravity, and the weight of the rod body 1A are adjusted using the change in diameter or diameter (taper angle). The mandrel 10 changes.

Specifically, in the above embodiment, the mandrel 10A whose diameter is gradually changed in the axial direction as schematically illustrated in Fig. 8A can be employed. In the mandrel 10A, portions 10a to 10e whose diameter gradually increases from the distal end H to the bottom end B are disposed in the axial direction with the steps 10f to 10i interposed therebetween. That is, the taper angles of the portions 10a to 10e are the same, but the diameters of the portions 10a to 10e are changed by arranging the steps 10f to 10i at every predetermined distance.

In the present embodiment, the mandrel 10B whose taper angle is gradually changed in the axial direction can be schematically illustrated as shown in FIG. 8B. The mandrel 10B includes portions 10j to 10n in which the taper angle gradually increases from the distal end H to the bottom end B. That is, the taper angles of the portions 10j to 10n are different and the taper angles of the portions 10j to 10n are changed every predetermined distance.

The reproducibility and accuracy of the mandrel 10B are superior to the mandrel 10A.

The volume and shape of the cavity S can be adjusted by the diameter of the adjustment portions 10a to 10e and 10j to 10n or the diameter variation (taper angle) in the mandrels 10A and 10B or the lengths of the portions 10a to 10e and 10j to 10n (steps) Change from 10f to 10i).

The winding width distribution of the prepreg 11 is adjusted to correspond to the change in volume and shape of the cavity S. That is, the area of the prepreg 11 wound on the mandrel 10A or 10B is adjusted in the axial direction to correspond to the volume and shape of the cavity S.

Therefore, the weight distribution, the center of gravity, the weight, and the like of the rod 1A molded in the mold 20 can be finely adjusted and easily adjusted without changing the mold 20. It is also possible to obtain the weight bow, the center of gravity, the weight, and the like of the rod 1A which are precisely adjusted without changing the outer shape or size of the rod 1A.

As described above, in the manufacturing method of the drawbar 1, the volume and shape of the cavity S can be changed without changing the mold 20 by using the mandrel 10 whose diameter or diameter change (taper angle) is gradually changed in the axial direction. In the case of fine adjustment and easy adjustment of the weight distribution, center of gravity and weight of the rod 1A molded in the mold 20.

In the pull rod 1, the weight of the rod 1A can be precisely adjusted without changing the outer shape or size of the rod 1A by gradually changing the diameter or diameter change (taper angle) of the axial hole 1b in the axial direction. Distribution, center of gravity and weight.

Therefore, according to the present embodiment, the plurality of bows of the stringer, the center of gravity, the weight, and the like, which are finely tuned to the stringer 1, can be provided to correspond to the user who uses the bow of the stringed instrument shown in Fig. 1 (stringed instrument player) Experience. The user can select and use the bow based on his experience.

The present invention is not limited to the above embodiment, but can be modified in various forms without Depart from the concept of the invention.

That is, the shapes of the mandrels 10A and 10B shown in Figs. 8A and 8B are merely examples of the present invention and the present invention is not limited to the shapes of the mandrels 10A and 10B.

For example, in the mandrel 10A shown in Fig. 8A, the configuration or the number of the portions 10a to 10e and the steps 10f to 10i having different diameters can be appropriately changed. In the mandrel 10A shown in Fig. 8A, the steps 10f to 10i can be inclined. Similarly, in the mandrel 10B shown in Fig. 8B, the configuration or the number of the portions 10j to 10n having different taper angles can be appropriately changed.

In the mandrels 10A and 10B shown in Figs. 8A and 8B, the diameters of the portions 10a to 10e and 10j to 10n may be set to different linear shapes or curved shapes. The volume of the cavity S can be combined with these shape changes.

That is, in the above manufacturing method, the mandrel 10 having a shape (tapered shape) in which at least the distal end H is thinner than the bottom end B as a whole can be used to take out the mandrel from the molded product (rod 1A). In particular, a mandrel obtained by changing the shape of the mandrel 10 within a range in which the required thickness (cavity S) of the rod body 1A can be obtained can be used.

When at least one of the weight distribution, the center of gravity, and the weight of the rod body 1A is adjusted, a plurality of types of mandrels 10 whose diameter or diameter change (taper angle) gradually changes in the axial direction can be prepared and the selected mandrel 10 can be used. Change the volume and shape of the cavity S.

In this case, a plurality of drawbars 1 having the same outer shape and size and having a weight distribution, a center of gravity, a weight, and the like are gradually adjusted.

The drawbar 1 according to the present invention is not limited to the above-described drawbar formed of CFRP, but a drawbar formed of GFRP or a CFRP and GFRP may be used. Combine the formed bow. The present invention can be widely applied to a drawbar formed using FRP of a composite material of fiber and resin.

The prepreg 11 is not limited to a thermosetting resin, but may be formed of a thermoplastic resin such as a nylon resin, a polycarbonate (PC) resin, and a polyphenylene sulfide (PPS) resin.

The drawbar 1 can be covered with a wood grain pattern. Therefore, an appearance similar to a wooden drawbar can be obtained.

The outer shape, size or the like of the drawbar 1 can be changed by changing the shapes of the recesses 21a and 22a formed in the mold 20 (the lower mold 21 and the upper mold 22).

While the preferred embodiment of the invention has been shown and described, it is understood that Additions, omissions, substitutions and other modifications may be made without departing from the spirit or scope of the invention. Therefore, the invention should not be construed as being limited to the embodiments described above, but only by the scope of the appended claims.

1‧‧‧ Pulling rod

1A‧‧‧ rod body

1a‧‧‧ head

1B‧‧‧Semi-finished products

1b‧‧‧Axial bore

2‧‧‧ bow root

3‧‧‧ bowstring

4‧‧‧ screws

10‧‧‧ mandrel

10-1‧‧‧ mandrel

10-2‧‧‧ mandrel

10-3‧‧‧ mandrel

10A‧‧‧ mandrel

Section 10a‧‧‧

10B‧‧‧ mandrel

Section 10b‧‧‧

Section 10c‧‧‧

10d‧‧‧section

Section 10e‧‧‧

10f‧‧‧

10g‧‧‧

10h‧‧‧

10i‧‧‧

Section 10j‧‧‧

10k‧‧‧section

Section 10l‧‧‧

10m‧‧‧ part

10n‧‧‧section

11‧‧‧Prepreg

11-1‧‧‧Prepreg

11-2‧‧‧Prepreg

11-3‧‧‧Prepreg

11a‧‧‧ inclined section

20‧‧‧Mold

21‧‧‧ Lower mold

21a‧‧‧ recess

22‧‧‧Upper mold

22a‧‧‧ recess

B‧‧‧Bottom

G1‧‧‧ position

G2‧‧‧ position

G3‧‧‧ position

H‧‧‧ distal end

X ₁ -X ₁ '‧‧‧ line

X ₂ -X ₂ '‧‧‧ line

1 is a plan view showing a bow of a stringed instrument according to an embodiment of the present invention.

2A, 2B, and 2C are a plan view of a bow of a stringed instrument shown in Fig. 1, a cross-sectional view taken along line X ₁ -X ₁ ', and a cross-sectional view taken along line X ₂ -X ₂ ', respectively. .

Figure 3 is a perspective view showing the manufacturing method of the drawbar shown in Figures 2A to 2C, wherein (a) of Figure 3 shows the state in which the prepreg is not wound on the mandrel and (b) of Figure 3 shows the pre-impregnation. The state in which the body is wound on the mandrel.

Figure 4 is a graph showing the relationship between the shape of the mandrel and the prepreg and the center of gravity of the molded body.

Figure 5 is a plan view showing a mold for making the drawbar shown in Figures 2A to 2C.

6 is a cross-sectional view showing the manufacturing method of the drawbar shown in FIGS. 2A to 2C, wherein (a) of FIG. 6 shows a state in which the semi-finished product is placed in a mold and (b) of FIG. 6 The state of the mold being clamped.

Figure 7 is a cross-sectional view showing the manufacturing method of the drawbar shown in Figures 2A to 2C, wherein (a) of Figure 7 shows the state in which the mandrel is taken out from the molded product (rod) and Figure 7 (b) shows the state in which the rod body (pull rod) is released from the mold.

Fig. 8A is a schematic view showing an example in which the diameter of the mandrel is gradually changed in the axial direction, and Fig. 8B is a view showing an example in which the taper angle of the mandrel is gradually changed in the axial direction.

1‧‧‧ Pulling rod

1a‧‧‧ head

1A‧‧‧ rod body

2‧‧‧ bow root

3‧‧‧ bowstring

4‧‧‧ screws

B‧‧‧Bottom

H‧‧‧ distal end

Claims (4)

A method for manufacturing a drawbar formed of a fiber-reinforced plastic for a stringed instrument, comprising the steps of: winding a prepreg formed by impregnating a fiber with a resin onto a mandrel having a diameter gradually decreasing toward a distal end Forming a semi-finished product formed on the mandrel with the prepreg in a mold; molding the semi-finished product to correspond to being formed in the mold by heating and pressurizing the semi-finished product in the mold a shape of one of the cavities with the mandrel; the mandrel is removed from the molded product molded into one of the shapes corresponding to the cavity to obtain a long and hollow body; At least one of a weight distribution, a center of gravity, and a weight of the shank of the shank is adjusted by changing the shape of the cavity using a mandrel whose diameter or diameter changes gradually in an axial direction. The method of manufacturing the drawbar of claim 1, wherein when adjusting the weight distribution, the center of gravity, and the weight of the shaft, the plurality of diameters or diameter changes can be gradually changed in the axial direction. The type of mandrel and the one of the plurality of types of mandrels are selectively used to change the shape of the cavity. The manufacturing method of the drawbar of claim 1 or 2, wherein the area of the prepreg wound on the mandrel is adjusted in advance based on the shape of the cavity. A drawbar for a stringed instrument and formed of a fiber-reinforced plastic stringed instrument, comprising: a rod having an axial bore that is reduced in diameter toward a distal end and molded into a long and hollow shape, wherein the diameter or diameter change of the shaft bore is gradually changed in an axial direction At least one of a weight distribution, a center of gravity, and a weight of the shaft of the shaft.